1. Field of the Invention
The invention pertains broadly to a method and apparatus for controlling the temperature of, and the flow of heat in, a metallic member such as copper piping. More particularly, the invention relates to a method and apparatus whereby the flow of solder between metallic members may be selectively limited and controlled.
Although it is susceptible to a variety of applications wherein it is necessary to control the temperature of or the heat flow in a heat conductive metallic member, the invention finds particular utility in soldering copper pipe ends together. Conventional soldering processes generally involve inserting the end of a pipe of a given diameter into the open end of a second pipe of a slightly larger diameter. The larger pipe is typically a fitting, which possesses a configuration enabling it to receive two or more pipe ends so as to orient the received pipe members at 180.degree., 90.degree., 45.degree., etc. to each other. Once the pipe ends have been inserted in the fitting, a flux material is applied to the fitting. The overlapping portion of the pipe end and fitting is then heated, typically by means of an oxygen acetylene torch, and a soldering material, usually a silver composition, is applied to the outside end of the overlapping portion at the end of the fitting. The melting points for typical silver soldering compounds require that the overlapping portion of the pipe end and fitting be heated to around 1250.degree. F. or more. This high heat, together with capillary action, results in the melted soldering compound being drawn axially between the overlapping pipe ends from the outside end of the overlapping portion to the opposite end of the overlapping portion within the fitting, being referred to as 100% flow. Indeed, the solder composition and/or the flux material often flows beyond the opposite end of the overlapping portion and protrudes into the interior of the fitting.
While 100% solder flow is acceptable in many cases, certain applications call for limiting the solder flow. For example, when the pipe members are designed to convey a high purity gas which might be contaminated by the exposed solder and/or flux materials, it is imperative that the flow of solder across the overlapping portion be confined to between 25% and 75% and, preferably, to 50% flow. Because the capillary force governing the flow of the solder between the overlapping pipe members is extremely strong, such force is difficult to impede. As such, selective termination of the solder flow has been heretofore difficult, if not impossible, to obtain on a reliable basis.
Prior art measures directed to solving the present problem have generally relied upon physical deformation of the pipe members so as to create a mechanical barrier or dam for terminating the solder flow. The latter methods are characterized by their complexity, adding additional extraneous steps to the otherwise simple soldering process, and by their failure to realize desirable standards of reliability and quality. In fact, such methods typically rely for their success upon the skill and expertise of a particular technician, acquired through countless hours of practice, and thus are prone to inconsistent results.
The subject invention addresses and overcomes the preceding problem by providing a method and apparatus for controlling solder flow which does not involve physical alteration of the pipe members, which is simple to execute and utilize, and which consistently achieves the highest degree of reliability and integrity. The present invention provides an apparatus for receiving a metallic member and being adapted to control the temperature of a selective portion of the metallic member for preventing the flow of solder and heat into the temperature controlled portion.
A further deficiency frequently associated with prior art soldering processes is that the extreme heat to which the copper piping is subjected causes it to become annealed and to lose some of its original strength. Metal which is heated expands and, when cooled, subsequently contracts. If the cooling is not uniform across the heated area, the member may become warped. This problem is intensified in a soldering process because the pipe members are only locally heated. As a result, undesirable dimensional changes in the members are common and the strength of the pipe members is compromised.
Moreover, copper alloy pipe members contain a small amount of cuprous oxide. In fusion welding and soldering processes, there is a redistribution of the cuprous oxide in the copper adjacent the soldered area or weld, at the point where the copper pipe closely approached the fusion temperature to which the member was heated. Consequently, there is a weakened zone adjacent the soldered joint, whereby the strength of the joint may be only 70% the strength of the copper base metal. Moreover, further weakening occurs when the heating flame carries hydrogen, as is the case with an oxygen acetylene torch. The hot hydrogen penetrates into the metal piping a few thousands of an inch back of the soldering line. The latter penetration reduces the cuprous oxide to form water vapor and disrupts the composition of the metal, producing a weakened zone adjacent the solder line which has only around 50% of the strength of the base metal.
The present invention effectively eliminates the creation of the aforementioned detrimental weakened areas in soldered copper piping. Relying as it does upon a thermal barrier for controlling the flow of heat through metal, the invention is able to successfully obtain an abrupt change in temperature directly adjacent a heated portion of copper tubing. When utilized in a process for soldering or welding pipe ends, the invention creates a temperature gradient at the pipe ends adjacent the heated overlapping portion, whereby solder is prevented from flowing beyond the thermal barrier and whereby the temperature of the area of the pipe ends immediately adjacent the solder line is controlled, so as to protect the base metal from the detrimental effects of heat. The invention realizes these and all of the foregoing objectives by presenting an apparatus for receiving a copper pipe fitting which has the end of a smaller diameter copper pipe inserted in at least one of its ends. The tool encloses a selective portion of the copper pipe fitting and has its side edges terminating at a point along the overlapping portion of the pipe end and the fitting which corresponds to the location beyond which it is desired to prevent the flow of solder. A coolant is directed into the interior of the tool, whereby the temperature of and the flow of heat in the overlapping portion of the pipe end and fitting is controlled. As a result, solder is prevented from flowing in the overlapped portion beyond the side edges of the tool.
2. Description of the Prior Art
It is known in the prior art to attempt to control the flow of solder in a pipe joint by deforming the pipe members to create a mechanical barrier to solder flow.
For example, U.S. Pat. No. 4,396,213, which issued on Aug. 2, 1983 to Hawkins teaches a method and joint wherein the flow of solder is limited in overlapped pipe ends by means of a circumferential groove formed in the exterior of the fitting creating an interior protrusion which tightly engages a groove formed on the exterior of the end of the inner pipe. No more than an insignificant amount of solder is allowed to flow beyond the interlocking grooves.
Similarly, Barnhart, et al. which issued on Apr. 18, 1950, teaches interengaging constrictions provided on outer and inner tubes, and which allow only a small amount of solder to flow into the space where the inner tube is gripped by the outer tube.
It is also known in the prior art to terminate the flow of solder between interfitting pipe ends by means of a seal created by abutting engagement between the pipe ends. U.S. Pat. No. 1,890,998 to Lindquist, for instance, dated Dec. 13, 1932, is directed to a joint wherein the inner pipe end is formed with a taper that tightly abuts against an interior shoulder formed in the outer pipe to seal off the interior of the outer pipe from the flow of solder. A variation of the latter joint is disclosed by U.S. Pat. No. 2,084,207, which issued to Lindquist, et al. on June 15, 1937. As shown therein, a tight joint is created between the inner pipe end and the interior of the outer pipe end by means of mating thread formations which prevent the entry of solder.
The prior art also teaches and makes known the concept of controlling the flow of a brazing filler alloy by means of a barrier consisting of an incompatible substance. Hikido, et al., U.S. Pat. No. 3,750,266 of Aug. 7, 1973, teaches the use of a flow control substance, such as a metal, applied to a surface to be brazed for confining the brazing alloy to a desired area. A similar teaching is provided by U.S. Pat. No. 3,667,109 to Alcenius, which issued on June 6, 1972 and wherein a contaminant is employed to prevent a melted brazing alloy from adhering to a portion of a fitting.
Additionally, the prior art discloses a method for controlling the flow of brazing alloy in order to avoid the disadvantages caused by annealing. In this regard, U.S. Pat. No. 3,198,556, issued on Aug. 3, 1965, to Kruse, et al. discloses inspection ports provided in a fitting to permit visual observation of the flow of a brazing alloy at the ports, whereupon the application of heat may be halted and the brazing alloy allowed to cool.
It is also generally known in the prior art to provide means for cooling a soldered joint or weld. Such means commonly involve inserting a cooling member or coolant source within the interior of a conduit which is being welded on its exterior surface. U.S Pat. No. 4,387,845, which issued on June 14, 1983 to Mefferd, shows a hollow cylindrical barrel which is adapted to have a hose coupling welded on its outer surface. An expanding mandrel is slidably inserted into the interior of the barrel, is positioned in radial alignment with the area to be welded, and is expanded to contact the interior surface of the barrel. A coolant is circulated through the mandrel to transfer heat away from the welded area.
U.S. Pat. No. 4,218,604 to Masaoka, et al., dated Aug. 19, 1980, teaches a method and apparatus for butt welding wherein a pair of pipe ends are welded, an insert is introduced into the interior of the welded pipe, and cooling medium is caused to flow in the pipe. The insert increases the velocity of the cooling medium so that maximum velocity occurs in the vicinity of the weld.
Similarly, Sloan, et al., U.S. Pat. No. 4,101,067, dated July 18, 1978, is directed to an expandable heat sink and sealing bladders for sealing the adjacent interiors of the ends of two pipes to be welded. Coolant is fed into the interior of the bladders to expand same and to cool the welded joint.
Similarly, U.S. Pat. No. 4,223,197, which issued to Imai, et al. on Sept. 16, 1980, discloses a rotatable nozzle for injecting a cooling medium against the inner surface of a pipe, the outer surface of which is being welded.
The prior art also makes known methods and devices for applying a coolant directly to a weld zone. For instance, U.S. Pat. No. 3,773,260 of Nov. 20, 1973 to Kunioka, et al., discloses a nozzle for directing a mist jet of cooling water and compressed air to a weld.
U.S. Pat. No. 3,948,428 to Bonomo, et al., dated Apr. 6, 1976, also teaches the combined use of water and gas to directly cool a weld. As shown therein, a pair of sliding blocks are arranged to face the weld, and nozzles provided in the blocks direct cooling water and gas to the weld. The sliding blocks serve to contain the molten bath for the weld.
It is further known in the prior art to utilize liquid nitrogen for cooling purposes. An example of this teaching is provided by U.S. Pat. No. 4,296,300 to Bottiglia, which issued on Oct. 20, 1981 and wherein a cooling saddle supplied with liquid nitrogen is arranged on a plate to be welded opposite the welding torch. During the formation of the weld, gaseous nitrogen escapes through holes in the saddle to cool a temperature degradable protecting coat applied to the plate prior to welding.
A welding chill which utilizes inert nitrogen gas is disclosed in U.S. Pat. No. 4,170,473 to Gerken and dated Oct. 9, 1979. The chill comprises a gas pervious body adapted to be supplied with an inert gas and applied to a welded area.
Finally, the prior art discloses a cooling box for covering the butt welded portion of a rail. As shown in U.S. Pat. No. 4,573,666, which issued to Nomura, et al. on Mar. 4, 1986, the cooling box includes a U-shaped box adapted to surround the welded portion of a rail, and which is divided into a plurality of independent cooling chambers. Each of the chambers is provided with a plurality of nozzles for directing cooling air toward the welded portion.
The prior art fails to teach or suggest a method and apparatus for controlling solder and heat flow in metallic pipe members which is characterized by a device for enclosing the area of pipe to be controlled, which is provided with an interior cavity for receiving a cooling substance, and which effectively and precisely prevents the flow of solder into the enclosed portion of the pipe members.